This invention relates to couplings for pipes and especially to couplings which effect a strong, reliable joint with a fluid-tight seal without the need for brazing or soldering.
The construction of piping networks requires couplings that can form fluid-tight joints between pipe ends which can withstand external mechanical forces, as well as internal fluid pressure and reliably maintain the integrity of the joint. Many forms of joints are known, such as brazed or soldered joints, threaded joints, welded joints and joints effected by mechanical means.
For example, copper tubing, which is used extensively throughout the world to provide water service in homes, businesses and industry, is typically joined by means of couplings which are soldered to the pipe ends to effect a connection.
The use of copper tubing for piping networks is so widespread that standard tubing sizes have been established in various countries. For example, in the U.S., there is the ASTM Standard entitled xe2x80x9cSpecification B88-99e1 Standard Specification for Seamless Copper Water Tubexe2x80x9d copyright 2001, in Germany, the DIN Standard and in the United Kingdom, the British Standard (BS) both of which are defined by the European Standard EN 1057, dated April, 1996 and entitled xe2x80x9cCopper and Copper Alloysxe2x80x94Seamless, Round Copper Tubes For Water and Gas in Sanitary and Heating Applicationsxe2x80x9d. Chart 1 below shows a portion of the range of outer diameters of the various standard copper tubes listed above.
Naturally, there are standard pipe fittings such as elbows (45xc2x0 and 90xc2x0), tees and straight segments matched for use with the standard tube diameters. These standard fittings are defined in the U.S. by ASME/Standard B16.22a-1998, Addenda to ASME B16.22-1995, entitled xe2x80x9cWrought Copper and Copper Alloy Solder Joint Pressure Fittingsxe2x80x9d, dated 1998. In Europe, the standard fittings are defined by EN 1254, dated Jul. 15, 1998 and entitled xe2x80x9cCopper and Copper Alloysxe2x80x94Plumbing Fittingsxe2x80x94Part 1 Fittings With Ends for Capilary Soldering or Capilary Brazing to Copper Tubesxe2x80x9d. The standard fittings have open ends with inner diameters sized to accept the outer diameter of a particular standard tube in mating contact for effecting a soldered joint.
In addition to the standard fittings described above, other components, such as valves, strainers, adapters, flow measurement devices, and other components which may be found in a pipe network will have a coupling which is compatible with the standard pipe, and it is understood that the term xe2x80x9ccouplingxe2x80x9d, when used herein, is not limited to a standard elbow, tee, or other fitting but includes the open end of any component useable in a piping network which serves to couple the component to the pipe end.
A soldered joint is effected between a standard diameter tube end and its associated standard fitting by first cleaning the surfaces to be joined, typically with an abrasive such as a wire brush or steel wool, to remove any contaminants and the oxide layer which forms on the surfaces. Next, the cleaned surfaces are coated with a flux material, usually an acid flux, which further disrupts the oxide layer (when heated) and permits metal to metal contact between the fitting, the pipe end and the solder. The pipe end is next mated with the fitting thereby bringing the cleaned, flux coated surfaces into contact. The fitting and pipe end are then heated to the melting temperature of the solder, and the solder is applied to the interface between the tube and the fitting. The solder melts, flows between the surfaces of the pipe end and the fitting via capillary action and forms the solder joint.
While the soldered joint provides a strong, fluid-tight connection between pipe end and fitting, it has several disadvantages. Many steps are required to make the soldered joint, thus, it is a time consuming and labor intensive operation. Some skill is required to obtain a quality, fluid-tight joint. Furthermore, the solder often contains lead, and the flux, when heated, can give off noxious fumes, thus, exposing the worker to hazardous substances which can adversely affect health over time. The joint is typically heated with an open gas flame which can pose a fire hazard.
To overcome these disadvantages, many attempts have been made to create mechanical couplings which do not require solder or flame to effect a strong, fluid-tight joint. Such mechanical couplings often use an over-sized opening accommodating an O-ring for sealing purposes and an annular ring interposed between the outer diameter of the pipe end and the inner diameter of the coupling to mechanically hold the parts together. The annular ring often has radially extending teeth which dig into the facing surfaces of the coupling and the pipe end to resist extraction of the pipe end from the coupling after engagement.
While these mechanical couplings avoid the above identified problems associated with soldered joints, they can suffer from one or more of the following disadvantages. The annular ring may not provide adequate pull-out strength, and the pipe end could be inadvertently separated from the coupling, for example, during thermal contraction of a long run made of several segments of mechanically coupled pipes. If both ends of the pipe run are fixed the thermal contraction will put significant tension loads on each joint, tending to pull them apart. If the pipes carry water and the water in the pipe freezes, the expansion of the water upon freezing will also put significant tensile load on the mechanical joints. Pressure spikes within the pipe, caused by a sudden closing of a valve (the xe2x80x9cwater hammer effectxe2x80x9d) also place the joints under tension, and could lead to a joint failure.
The annular ring also does not help keep the pipe end concentric with the coupling upon insertion, allowing the pipe end to tip and deform the annular ring and gouge the inside surface of the coupling or an elastomeric seal, such as an O-ring. The annular ring cannot be relied upon to provide electrical continuity between the pipe end and the coupling, sometimes resulting in a relatively poor ground for electrical purposes. In such a joint, there is furthermore little or no resistance to axial rotation of the pipe relatively to the coupling (i.e., relative rotation of the pipe and coupling about the longitudinal axis of the pipe). Thus, valves or other items mounted on the pipe will tend to rotate. Use of an enlarged section to accommodate the annular ring may cause energy loss impeding fluid flow if the fluid is forced to flow into a coupling having a larger cross-sectional area. In general, when mechanical couplings are designed to overcome the aforementioned inherent disadvantages, they tend to suffer from a high part count, making them relatively complex and expensive.
The invention concerns a coupling for engaging a pipe end without the use of solder. The coupling comprises a first receptacle, preferably cylindrical in shape for receiving the pipe end, and a second receptacle, also preferably cylindrical, arranged coaxially and in tandem with the first receptacle. The second receptacle is smaller than the first receptacle so as to form a shoulder within the coupling between the first and second receptacles.
The coupling also includes a retainer having a perimetrical surface, preferably cylindrical and positioned within and coaxial with the first receptacle. Locking teeth are positioned circumferentially around the retainer and project from the perimetrical surface, the locking teeth being engageable with the first receptacle and the pipe end to resist removal of the pipe end from the coupling.
An elastomeric seal, for example an O-ring, is positioned coaxially within the first receptacle between the shoulder and the retainer and effects a fluid-tight seal between the pipe end and the first receptacle.
In the preferred embodiment of the invention, each of the locking teeth has a first edge facing toward the shoulder and a second edge positioned opposite thereto. Each of the locking teeth is resiliently angularly biased to position the first edges radially inwardly of the perimetrical surface of the retainer and the second edges radially outwardly thereof. The first edges are engageable with the pipe end to resist relative motion between the pipe end and the retainer in a direction away from the shoulder, and the second edges are engaged with the first receptacle for resisting relative motion between the retainer and the first receptacle in a direction away from the shoulder. The pipe end is insertable under the first edges in a direction toward the shoulder for insertion into the fitting.
A circumferential groove is preferably positioned within the first receptacle adjacent to the locking teeth. Each of the second edges is resiliently biased into engagement with the groove providing even greater resistence to motion of the retainer relative to the first receptacle in a direction away from the shoulder.
In an alternate embodiment, the retainer includes a first plurality of the teeth that are resiliently biased radially inwardly from the perimetrical surface of the retainer. The first plurality of teeth each have an edge facing toward the shoulder, each edge being engageable with the pipe end. The first plurality of teeth deflect resiliently radially outwardly to allow insertion of the pipe end coaxially into the coupling, the edges being resiliently biased into engagement with the pipe to resist relative movement between the pipe and the retainer in a direction away from the shoulder.
A second plurality of the teeth each have a first segment resiliently biased radially inwardly from the perimetrical surface and a second segment extending angularly from the first segment outwardly from the perimetrical surface. The first and second segments define an apex located between the segments, and each apex is engageable with the pipe end to support it upon its insertion coaxially into the coupling. Each second segment also has an edge facing away from the shoulder for engaging the first receptacle. The second plurality of teeth resiliently deflect radially inwardly to allow insertion of the retainer coaxially into the first receptacle. The edges on the second segments are resiliently biased into engagement with the first receptacle to resist relative movement between the retainer and the coupling in a direction away from the shoulder.
The retainer preferably has a first end facing the shoulder and a second end oppositely arranged. A first flange is positioned on the first end and extends radially inwardly from the perimetrical surface. Together, the first flange and the shoulder define a pocket for containing an elastomeric seal such as and O-ring. A second flange is positioned on the second end and extends radially outwardly from the perimetrical surface. The second flange engages the first receptacle and limits motion of the retainer into it.
To afford a more positive engagement between the teeth and the pipe end in both the preferred and alternate embodiments, a circumferential groove may be located along an outer surface of the pipe end and positioned for engagement with the edges of the teeth. The edges are resiliently biased into the groove upon engagement between the coupling and the pipe end and provide even greater resistance to motion of the pipe end relatively to the coupling in a direction away from the shoulder. A second circumferential groove is preferably located on the pipe end in spaced relation to the first groove. The second groove is positioned to align coaxially flush with an end of the retainer when the edges of the aforementioned teeth are engaged with the first groove, thus, giving a visual indication that the pipe end is properly engaged with the coupling.
Preferably, the standard copper fitting is chosen from among the ASTM standards but could also comprise DIN or BS standard fittings as well.
It is an object of the invention to provide a mechanical pipe coupling which does not require solder to effect a fluid-tight joint.
It is another object of the invention to provide a pipe coupling which can be readily formed from ASTM, DIN or BS standard fittings.
It is another object of the invention to provide a pipe coupling which is simple to make, simple to use and has a low part count.
It is still another object of the invention to provide a pipe coupling having a relatively high pull-out strength.
It is yet another object of the invention to provide a pipe coupling which helps to concentrically align the coupling and pipe upon insertion of the pipe end into the coupling.
It is again another object of the invention to provide a coupling which maintains good electrical conductivity across the joint.
It is yet again another object of the invention to provide a coupling which causes low energy loss to fluid flowing through it.
It is still again another object of the invention to provide a coupling which effectively resists axial rotation of the pipe relatively to the fitting.
These and other objects of the invention will become apparent from consideration of the following drawings and detailed description of preferred and alternate embodiments of the coupling according to the invention.